1. Technical Field
The disclosure generally relates to heat transfer apparatuses, and particularly to a loop heat pipe with a high heat transfer efficiency.
2. Description of Related Art
Loop heat pipes are widely used in various fields for heat dissipation purposes due to their excellent heat transfer performance. A commonly used loop heat pipe includes an evaporator thermally attached to a heat-generating electronic component, a condenser, and a vapor line and a liquid line respectively interconnected between the evaporator and the condenser. A predetermined quantity of bi-phase working medium is contained in the loop heat pipe. A wick structure, lining an inner surface of the evaporator, draws condensed working medium back to the evaporator after the working medium in vaporized form has condensed at the condenser.
In operation of the loop heat pipe, the working medium conveys heat from the evaporator to the condenser. More specifically, the working medium in a liquid state contained in the wick structure of the evaporator absorbs heat from the heat-generating electronic component and vaporizes to the vapor state. The working medium in the vapor state moves through the vapor line toward the condenser, carrying heat with it. At the condenser, the working medium in the vapor state dissipates the heat to the ambient environment and condenses back to the liquid state, and then flows back to the evaporator through the liquid line to start another heat transfer cycle.
If the wick structure of the evaporator is too thick, the working medium in the liquid state contained in the wick structure of the evaporator cannot be completely vaporized in a timely manner. Therefore, part of the working medium in the liquid state mixes with the working medium in the vapor state to form a number of bubbles in and on the wick structure of the evaporator. The bubbles tend to block the pores of the wick structure of the evaporator and decrease a capillarity of the wick structure, to thereby retard the flow of the condensed working medium in the liquid state back into the evaporator. Thus, the amount of working medium in the liquid state contained in the wick structure of the evaporator is decreased, which may eventually result in overheating of the loop heat pipe.
On the other hand, if the wick structure of the evaporator is too thin, the working medium contained in the wick structure is liable to dry off altogether, whereupon the loop heat pipe is destroyed.
What is needed, therefore, is a loop heat pipe which can overcome the described limitations.